Cooperative
Extension
Service


University of Illinois
at
Urbana-Champaign


No. 17/July 16, 1998

Preharvest Intervals and Rotational Crop Restrictions of Soybean Herbicides

Applications of postemergence soybean herbicides have been completed in many areas of the state. While the results of these applications have ranged from excellent weed control to excessive crop injury, the window for making these applications is rapidly closing. Undoubtedly, however, some soybean fields will be retreated for one of a number of reasons.

Almost all postemergence soybean herbicides have certain restrictive time intervals specified on their respective labels. Preharvest intervals specify the amount of time that must elapse between herbicide application and crop harvest. These intervals are established to allow sufficient time for the crop to metabolize (break down) the herbicide so residue levels do not exceed those originally established when the herbicide received its label. Failure to observe the specified preharvest interval could potentially result in herbicide residues present in the crop in excess of the legal limit. Table 1 contains information about preharvest intervals for many soybean herbicides.

Table 1. Preharvest intervals and grazing retrictions for postemergence soybeanherbicides.
HerbicidePreharvest
interval
(days)
Feed or graze forage?
Postemergence--
Grass only
Assure II/Matador80No!
Fusilade DXPrebloomNo!
FusionPrebloomNo!
Poast Plus/Prestige75Hay?
Select60No!
Postemergence--
Broadleaf, contact
BasagranNoneYes
Blazer/Status50No!
Cobra45No!
Flexstar HLPrebloomNo!
Galaxy50No!
ReflexPrebloomNo!
Resource60No!
Stellar60No!
Storm50No!
Postemergence- -
Broadleaf, systemic
Butyrac (2,4-DB)60Yes/PHI
Classic60No!
FirstRate65Yes?
Pinnacle60No!
Pursuit85No!
Raptor85No!
Roundup Ultraa14Yes -- 7/14
Scepter90No!
Scepter O.T.90No!
Synchrony STS60No!
Touchdown 5b60No!
Harvest-aid use
Gramoxone ExtraNAYes -- 15 days
Roundup Ultra7>25 days

aUse as broadcast treatment only with Roundup Ready-designated soybean varities.
bMay be used as a spot treatment. Use NIS with wiper applications of Touchdown 5 but not with Roundup Ultra.

Another time interval to observe is the rotational crop interval. Most herbicide labels have rotational crop tables that specify the amount of time that must elapse between herbicide application and planting of the rotational crop the following season. These intervals are specified to reduce the possibility that sufficient herbicide residue persists long enough in the soil to have an adverse impact on the following rotational crop. Some herbicide rotational restrictions are based solely on time, while other factors (such as soil pH and amount of precipitation received after herbicide application) influence the length of the crop rotational interval. For example, the Scepter label (region 2) indicates that "field corn may be planted in the spring of the year following a Scepter application unless extreme drought conditionsdevelop,"defined as less than 15 inches of precipitation received from 2 weeks prior to the date of last application through November 15 of the same year. Field corn may be planted 9 months after application of Classic, but this interval is extended 2 additional months if applications containing chlorimuron are made after August 1. Table 2 contains rotational crop intervals for soybean herbicides.

Table 2. Soybean herbicide recropping restrictions, months.
HerbicideCommentsCornSorghumWheatOats
Chlorimuron andsome of its premixes
Canopyaw/metribuzin1012430
Classic/Skirmishchlorimuron
(hi)
9b9b33
Synchrony STSw/thifensulfuron9b9b33
Flumetsulam
and its premixes;
cloransulam
Broadstrike + Dualw/metolaclorAT124.54.5
Broadstrike +
Treflan
w/trifluralin812412
FirstRatecloransulam99330
PythonflumetsulamAT12444
Imazaquin and its
premixes (full rate =
Detail, Squadron, Tri-Scept)
Scepter--
Region3c
imazaquin18111818
Scepter--Region 3c0.5 rate--
post
NYe11FalleNYe
Scepter--
Region 2c
imazaquin9.5d,e11e3e11e
Detail--Region 2cw/dimethenamid9.5d,e11e4e11e
Squadron--Region 2cw/pendimethalin9.5d,e11e4e11e
Triscept--
Region 2c
w/trifluralin9.5d,e11e4e11e
Imazethapyr and its
premixes (full rate =
Pursuit, Pursuit Plus;
Steel = Pursuit Plus +
0.5X Scepter)
Pursuitimazethapyr8.5f18418
Pursuit Plusw/pendimethalin8.518418
Steel--Region 2cAbove +
imazaquin
9.5d,e18e4e18e
Sulfentrazone alone
or plus chlorimuron
Authority
First
sulfentrazone1010?430
Authority
Broadleafa
w/chlorimuron1010430
Canopy XLaw/chlorimuron1010430
Other active
ingredients
Command 3MEclomazone991212
Flexstar HL, Reflexfomesafen101844
Raptorimazamox9939
Sencor, Lexonemetribuzin412412
Turbometribuzin8124.512

HerbicideCommentsRyeAlfalfaCloverSoybeans
Chlorimuron and some
of its premixes
Canopyaw/metribuzin41012AT
Classic/Skirmishchlorimuron (hi)312b12bAT
Synchrony STSw/thifensulfuron312b12bAT
Flumetsulam and its
premixes; cloransulam
Broadstrike +
Dual
w/metolaclor4.5426FbaAT
Broadstrike +
Treflan
w/trifluralin4426FbaAT
FirstRatecloransulam30930FbaAT
Pythonflumetsulam426FbaAT
Imazaquin and its
premixes (full rate =
Detail, Squadron, Tri-Scept)
Scepter--
Region 3c
imazaquin181818AT
Scepter--Region 3c0.5 rate-post181818AT
Scepter--
Region 2c
imazaquin181818AT
Detail--
Region 2c
w/dimethenamid181818AT
Squadron--
Region 2c
w/pendimethalin181818AT
Triscept--
Region 2c
w/trifluralin181818AT
Imazethapyr and its
premixes (full rate =
Pursuit, Pursuit Plus;
Steel = Pursuit Plus +
0.5X Scepter)
Pursuitimazethapyr4440AT
Pursuit
Plus
w/pendimethalin9.59.540AT
Steel--Region 2cAbove +
imazaquin
401840AT
Sulfentrazone alone or
plus chlorimuron
Authority
First
sulfentrazone4?1218AT
Authority BR>Broadleafaw/chlorimuron41218AT
Canopy XLaw/chlorimuron41218AT
Other active
ingredients
Command 3MEclomazone121212AT
Flexstar HL,
Reflex
fomesafen41018AT
Raptorimazamox4918AT
Sencor,
Lexone
metribuzin124124
Turbometribuzin1212128


Fba = Field bioassay needed (see label), NY = next year, 2Y = 2nd year, NL = not labeled
aMidwest states' rate, soil pH <6.8.
bExtend 2 months if applied after August 1.
cSee label for exact area and Region 3 (northern Illinois) full-use rate.
d10- to 15-inch annual rainfall required or use IMI corn hybrids.
e15 months if Scepter/Scepter OT sequence, but 9.5 months or NY for IMI corn hybrids.
fIMI-designated corn hybrids may be replanted AT.

Aaron Hager (hagera@idea.ag.uiuc.edu) and Marshal McGlamery (mmcglame@uiuc.edu), Crop Sciences, (217)333-4424